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DFW Herpetological Society - Herp of the Month
Spring 2004


The DFW Herpetological Society is a group with a mission - to promote understanding, appreciation and conservation of reptiles and amphibians, and to encourage respect for their habitats.

If you want to learn about native species and recognize venomous snakes, this is the group for you!  Interested in observing and photographing reptiles and amphibians in the wild?  DFW Herpetological Society members enjoy field trips to local destinations as well as weekend-long expeditions to locations such as the Hill Country and Trans Pecos.

Anyone interested in herps is welcome at their meetings!  Meetings are held the 3rd Saturday of the month at 7:00pm, in the UTA Life Sciences Building, Room 119.  Check out www.dfwherp.org to learn about this great group!


This article is reprinted with permission of the DFW Herpetological Society.
Author Charla Sells


Nerodia harteri harteri

Five years ago I had a fear of anything I considered "icky." Since then I have grown to understand and enjoy the variety of reptiles and amphibians that I have had the pleasure to encounter. My main interests now include native species and the conservation of their habitats. Among these animals is one that is on my life list, the Brazos Water Snake, which is listed as a threatened species in Texas.

Jerry Shelton remembers when he was younger seeing one of these snakes and not being very interested in them at the time. Since then he has learned much about them and has been actively searching for them. Unfortunately we did not had much luck in finding them at first, but we were more successful later. On a Friday afternoon in 2002 we headed to a canoe rental place on the Brazos River and planned to spend the weekend on the river herping, specifically looking for the Brazos Water Snake. While Jerry was there he decided to go ahead and look for herps along the banks. He had not been there five minutes when he spotted a small water snake. He quickly picked it up and to his amazement it was a small Brazos Water Snake. This snake was probably only a few weeks old, as it still had the slit from the umbilical cord. Finding this little snake in a somewhat populated area does give us hope that maybe one day they will be removed from the threatened species list.

Description
The Brazos water snake can be distinguished from its more common counterparts, the blotched water snake (N. erythrogaster transersa) and the diamondback water snake (N. rhombifer). The dorsal color ranges from dark green or olive to brown or dark gray. They sometimes appear to have stripes running the length of their bodies. These stripes are the result of two rows of dark spots or crossbars on their back or sides. Ventral coloration ranges from orange to pink with a row of dark spots running along each side. Their scales are keeled with 21-25 rows at midbody; their anal plate is divided. They also have 2 rows of small scales between the posterior chin shields, and range in length anywhere from 16 inches to 32 inches.

Habitat & Behavior
These snakes can only be found along a 182-mile stretch of the Brazos River and its tributaries, including Possum Kingdom Lake and Lake Granbury. They prefer the fast moving water, especially the riffles, with the young staying close to the shallow riffles. The Brazos Water Snake is unlike many other water snakes when being approached by man. Most snakes will seek shelter underneath a rock or some other nearby surface object; these snakes will immediately head for the opposite shore. Once there they will either stay submerged or with only their heads up move along the shoreline.

Most of these snakes can be observed either in the water or on land within 10 feet of the water. The smaller snakes can often be found near the shallow riffles and are rarely found with any adults. They have been observed anchoring to rocks with their tails when hunting for food. The adults can be found in the deeper parts of the riffles and when not foraging can be found under larger rocks or in holes along the shoreline. As far as their preferred habitats in lakes, they are usually found within 4 feet of the water edge. They have been known to be coiled under boats along the beaches and even boat sheds. With the creation of lakes along the Brazos River, the flow of the river has changed causing fewer shallow riffles. There was much concern that with the disappearance of the shallow riffles, the Brazos Water Snake would also disappear. However, this snake has shown that it has the capability to adapt to lake habitats.

Abundance and Reproduction
They remain elusive creatures and therefore not much is known about their numbers. However, efforts are currently underway to try and increase the numbers in the wild population. It is known that mating takes place in the spring, with live births occurring in late summer to early fall. They typically will have anywhere from 7 to 23 young, which range in length from 6 inches to 10 inches long.

Notes
They seem to be primarily diurnal, feeding on fish and amphibians comparable to their size. While they do seem to be adapting to the changes in some parts of their habitats in others they appear to be declining (Mara, 1995). The construction of reservoirs may be a contributing factor in their decline in these areas. Although little seems to be known about them there is another water snake that is similar; it is the Concho Water Snake (N. harteri paucimaculata). The Concho Water Snake is also habitat-specific and can only be found on the Concho river and its tributaries. It is also recognized federally as a threatened species due possibly to the construction of a dam near its home. The Concho Water Snakes' numbers are thought to be somewhere between 300-700. They also seem to be adapting to the changes in their habitat, which gives hope that the Brazos Water Snake may recover.


Literature Cited:

  • Mara, W.P. 1995. Water Snakes of North America. Pp.18-19.
  • Bockstanz, Lori M. and David C. Cannatella. 2000. Herps of Texas, www.zo.utexas.edu/research/txherps.
  • Werler, John E. and James R. Dixon. 2000. Texas Snakes. Pp. 207-209.


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